Calcium is an essential nutrient and the most abundant mineral in the human body. Calcium plays a vital role in building healthy teeth and bones, blood clotting, muscle contraction, nerve function and heart function. In addition to these benefits, it has recently been suggested that calcium reduces the risk of recurrence of colon polyps. See Baron J. A. et al. New England Journal of Medicine 1999; 340: 101–107.
Most importantly, calcium reduces the risk of bone loss caused by osteoporosis in both men and women, a condition that afflicts more than 44 million individuals in the United States alone. With an aging population in the United States, it is estimated that the figure will rise to more than 61 million by the year 2020. This growing health crisis is largely a result of calcium deficiency in the diet.
In recognition of the benefits of calcium, doctors recommend high daily calcium intakes for people of all age groups. For example, the National Academy of Sciences (“NAS”), Institute of Medicine recommends the daily calcium intakes shown below.
National Institute of Sciences, Institute of Medicine DietaryReference Intake (DIR) of Calcium for Men And WomenAgeDRI1–3years  500 mg4–8years  800 mg9–18years1,300 mg19–50years1,000 mg51years and up1,200 mg
Similarly, the United States Recommended Daily Allowance (“USRDA”) of calcium for adults is 800 to 1,400 mg.
It has been estimated, however, that half of all Americans do not consume sufficient amounts of calcium. More troubling, 80% of women, the group at highest risk for developing osteoporosis, do not consume enough calcium. Further, estimates reveal that only 20% of girls and 50% of boys between the ages of 9 and 19 get the recommended daily intake of calcium. This is particularly troubling since 90% of human bone mass is developed by age 17. Thus, proper calcium consumption during these years is critical for preventing the onset of osteoporosis in later life.
For many individuals, it is difficult to meet the large daily intake of calcium suggested by physicians from dietary sources alone. This calcium deficiency is due in part to the low calcium content of foods that comprise the typical diet. Multi-vitamins and calcium supplement tablets represent an important alternative to dietary calcium. However, most commercially available multi-vitamin tablets provide only 10 to 20% of the recommended dose calcium. Calcium supplement tablets provide more calcium, typically 500 to 600 mg. To meet the recommendations, two tablets must be consumed daily. Unfortunately, too few people adhere to calcium supplement regimens, owing in part to the fact that presently available calcium tablets are very large and difficult or uncomfortable to swallow.
Milk is widely recognized as a good source of calcium. Several glasses of milk must be consumed each day in order to obtain sufficient calcium. For example, 9 to 18 year old children must consume at least four glasses of milk daily in order to receive the proper amount of calcium. However, the popularity of carbonated beverages has resulted in a decline in milk consumption among children. Further, many individuals who suffer from lactose intolerance cannot drink milk. Other individuals choose not to drink milk due to its high saturated fat content.
Health conscience consumers are increasingly demanding alternative sources of calcium from dietary products. This is evident from a recent study by Mintel's International showing an increase in food and drink products sold in North America which advertise calcium content. According to that study, 32% of dairy products, including milk and cheeses, 27% of beverages, and 18% of snacks advertise calcium content. In contrast, only 5% of bakery products noted calcium content. This is unfortunate since bread and cereal products are the most ubiquitous food source worldwide. For example, the U.S. Department of Agriculture estimates that approximately 200 pounds of flour and cereal products were consumed per capita in the United States in 2001, a figure which has been steadily growing for the past three decades. In contrast, only 22 gallons of milk were consumed per capita in the United States during the same period. Clearly, bread products would provide an ideal vehicle to supplement dietary calcium intake.
Unfortunately, conventional breads represent a poor source of calcium. The total mineral content of wheat generally ranges from 1 to 2% by weight. The minerals present in wheat are primarily distributed in the bran and are present in the endosperm, the wheat fraction from which most commercial flours are produced, to a much smaller degree. For instance, wheat typically contains about 0.45% by weight elemental calcium. The bran fraction contains about 0.128% by weight elemental calcium, whereas flour fractions such as farina, patent flour, and clear flour contain less than 0.03% by weight calcium. Breads made from these conventional flours will obviously contain only a small fraction of the recommended daily calcium intake.
It is conventional in the baking industry to add sources of calcium to bread products as “dough conditioners.” Typically, calcium sulfate or calcium carbonate is added to dough in order to regulate pH and increase the electrolytic strength of soft water to prevent soft or sticky dough. Such calcium dough conditioners are usually added to dough from about 0.1 to 0.6% by weight. These calcium dough conditioners are not present in sufficient amounts to contribute significantly to the calcium value of the resulting bread products.
Calcium sulfate and calcium carbonate cannot be added directly to dough in sufficiently large amounts to contribute to the calcium content of bread due to inherent limitations imposed by the chemistry of the dough. In the fermentation process that occurs in leavened breads, pH plays a critical role in controlling yeast activity, amylolytic activity, and gluten behavior. The pH of bread typically ranges from about 5.1 to about 5.4. To reach these final pH levels, the dough must have final pH level as low as 4.5 to 5.2, however the pH must drop even lower during the fermentation process.
For example, in the typical commercial production of leavened bread by the sponge-dough process, the pH of the initially mixed sponge ingredients is about 5.3. As the fermentation process proceeds, the pH will rapidly drop over the first two hours of incubation. The drop in pH is principally the result of the lactic, succinic, and acetic acids produced by fermentation. Over the next two hours of fermentation, the pH will stabilize to a final value of about 4.7. When the remaining dough ingredients are added to the sponge, the pH will quickly rise back to its initial value of about 5.3 due to the diluting and buffering effects of the added flour. Subsequent fermentation again results in pH drop to a final value of about 5.0. As the dough is baked, volatilization of the fermentation acids causes the pH to rise to a final value of about 5.4 in the finished bread product. Some specialty breads such as French bread may have a pH as low as about 3.8 to 4.0, requiring even lower pH drops during the fermentation process.
Calcium salts such as calcium carbonate, calcium sulfate, and calcium citrate exert a buffering effect on dough chemistry by reacting with the organic acids produced during fermentation. Even relatively low levels of these calcium salts will prevent the pH from dropping during fermentation, interfering with the functioning of yeast and altering the flavor and texture of the resulting bread product. At higher levels, these salts can result in dough with a basic pH. Despite its low solubility in water, a saturated aqueous solution of calcium carbonate has a pH between 9 and 10 at ambient temperatures. Thus, calcium carbonate cannot be added directly to dough without upsetting the acidic pH characteristic of most bread dough. Further, the very low water solubility of calcium carbonate can result in granular precipitates when added in large quantities to dough. For these reasons, it is not adequate to fortify bread products by directly adding traditional calcium salts to dough.
To date, efforts to increase the calcium content of bread by other methods have met with only limited success.
U.S. Pat. No. 5,108,764 to Craig discloses the dough-up stage addition of calcium carbonate for its nutritive value in the production of reduced fat or no-added fat crackers. The amount of added calcium carbonate is described as “minor.”
U.S. Pat. No. 6,126,982 to Maldonado discloses bread products having increased calcium contents produced from flours having large amounts of added middlings. That patent purports to provide bread products having up to 200% of the USRDA calcium dose per serving. However, the usefulness of the method disclosed by Maldonado is limited by the requirement of middling addition, since many commercial breads require highly purified flours.
U.S. Pat. No. 5,514,387 to Zimmerman, et al. discloses crackers and other baked goods providing greater than 10% of the USRDA calcium dose. The disclosed process uses emulsifier compositions such as combinations of polysorbate 60 and sodium stearoyl lactylate to reduce hardness and dry mouthfeel caused by the addition of insoluble calcium salts such as calcium carbonate. The fermented crackers produced by the method disclosed in this patent are reported to have pH values between 6.6 and 8.2, far higher than the tolerable pH of a typical commercial baked bread product.
U.S. Pat. Nos. 4,859,473 and 5,066,499 to Arciszewski et al disclose the addition of calcium carbonate to the dough-up stage in a process for preparing low sodium crackers and cookies. Calcium carbonate is added for its nutritive value in amounts up to about 10% by total weight. The resulting pH of the disclosed baked goods, between 6.5 and 8, is higher than the tolerable pH of most commercial baked bread products.
U.S. Pat. No. 6,210,720 to Leusner, et al. discloses lightly cooked cereal dough products fortified with at least 0.3% calcium. The disclosed process involves the addition of calcium carbonate having a small average particle size and a calcium sequestering agent such as phosphate salts or citric acid to a traditional cereal dough. The calcium carbonate and the calcium sequestering agent are added to the dough in conjunction with a wet blend. Calcium fortification of leavened bread products is not disclosed.
U.S. Pat. No. 5,945,144 to Hahn, et al. disclosed calcium fortified pasta produced by adding calcium salts such as calcium citrate to pasta dough before extrusion. The methods disclosed would not be applicable to prepare highly calcium fortified leavened bread products.
U.S. Pat. No. 5,260,082 to delValle, et al. discloses a calcium citrate additive for baked goods. The calcium citrate is prepared by reacting citric acid with calcium hydroxide or calcium carbonate in aqueous solution followed by spray drying to produce fine calcium citrate crystals. The calcium citrate crystals are added directly to the sponge to produce bread products alleged to have improved volume, shelf-life, and microwavability as compared to both control breads not having the additive and bread products prepared from commercially available calcium citrate. U.S. Pat. No. 5,260,082 does not disclose addition of calcium citrate to bread products for its nutritional value.
It would be desirable to enrich a variety of bread products with calcium in sufficient quantities to supply the recommended daily calcium dose. To this end, it would be desirable to enrich bread with calcium carbonate, since calcium carbonate is the most abundant and cost-efficient source of elemental calcium.
It is therefore an object of the present invention to provide bread products fortified with calcium, particularly in the form of calcium carbonate.
It is a further object of the present invention to provide calcium-fortified bread products having organoleptic properties, crumb structure, volume, and mouthfeel comparable to conventional breads.
It is a further object of the invention to provide calcium additives and methods for fortifying bread products with calcium additives.